Evaluation of Depositional Mechanisms in Sediment-Hosted Micron Gold Deposits

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9523771 Kesler This proposal requests support for an evaluation of processes that could deposit gold in sediment-hosted micron gold (SHMG) deposits. Despite their importance, we lack comprehensive models for gold deposition in these ores, largely because we do not understand the mineralogical form of gold in the ore and its relation to geologic features. In order to evaluate the feasibility of the solid solution/adsorbtion/electrochemical depositional processes for SHMG deposits, we need to know: 1) the geologic setting of pyrite with different textures and gold contents; 2) the degree to which overgrowths on pyrite can be correlated; 3) the form of gold in pyrite. Efforts to answer these questions will focus on deposit-scale studies at the large Twin Creeks deposit in Nevada, which contains widespread pyrite textures of the type described here. Work will also include a reconnaissance survey of the distribution of pyrite in Paleozoic sedimentary rocks of northern Nevada to test the importance of pre-existing pyrite to gold deposition. In addition to their obvious importance to genetic theories, results could aid exploration by forecasting grades and delimiting targets during early stages of drilling.